Resonant Bridge Power Converter for Light-Load Efficiency

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Solution Overview

Problem

Existing power converters face challenges in achieving high conversion efficiency, especially in light load conditions, due to the loss incurred from the charge stored in snubber capacitors.

Innovation Solution

The power converter incorporates external connection terminals, bridge circuits, an inductance element, and a controller, with a capacitor connected in a closed-loop circuit. The controller drives the switching elements at a frequency higher than the resonant frequency of the closed-loop circuit, reducing current values at switching times and enhancing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If snubber capacitors are used to suppress voltage spikes and protect switching elements, then reliability is improved, but conversion efficiency deteriorates due to charge loss in light load conditions

Engineering Contradiction:

Improveprotection of switching elementsVSAvoidconversion efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts the protective function from the snubber capacitor and relocates it to a capacitor connected in parallel with the inductance element. This separation allows the original snubber capacitor to be removed or reduced, eliminating its energy loss in light load conditions while maintaining voltage spike suppression protection through the newly positioned capacitor.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a capacitor as an intermediary element connected in parallel with the inductance element. This intermediary capacitor serves dual purposes: it suppresses voltage spikes to protect switching elements and does not cause energy loss in light load conditions, thereby resolving the contradiction between reliability and conversion efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If switching frequency is increased to improve productivity, then conversion efficiency is improved, but switching losses increase

Engineering Contradiction:

Improveconversion efficiencyVSAvoidswitching losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent utilizes resonant vibration of the LC circuit formed by the inductance element and the capacitor connected in parallel with it. By operating at or near the resonant frequency, the circuit achieves natural oscillation that reduces switching losses while maintaining high conversion efficiency and productivity.

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent changes the operating parameters by connecting a capacitor in parallel with the inductance element to form a resonant circuit. This parameter change allows the system to operate at resonant frequency, optimizing the balance between productivity and switching losses.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If transformer current waveform is improved to approach sinusoidal shape, then conversion efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveconversion efficiencyVSAvoidcircuit configuration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the functions of voltage spike suppression and current waveform improvement into a single capacitor connected in parallel with the inductance element. This unified approach achieves sinusoidal current waveform and high conversion efficiency without requiring additional complex circuitry.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The capacitor connected in parallel with the inductance element serves multiple functions simultaneously: it suppresses voltage spikes, improves transformer current waveform to sinusoidal shape, and enables resonant operation. This multi-functionality achieves high conversion efficiency without increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration results in a higher conversion efficiency over a wide range of loads by reducing switching losses and improving the waveform of transformer currents, which approaches a sinusoidal shape.

Implementation Method 1

the closed-loop circuit has a capacitor connected between the inductance element and at least one of respective AC terminals of the two bridge circuits. The controller drives the switching elements at a switching frequency higher than a resonant frequency of the closed-loop circuit.

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20250158529A1Power converter and non-transitory computer readable medium

Publication Date: 2025.05.15 DENSO CORP

AI summary

A power converter includes external connection terminals, bridge circuits, an inductance element and a controller. The bridge circuits are connected to the external connection terminals, respectively. The inductance element is connected between an AC terminal of one of two of the bridge circuits and an AC terminal of another one of two of the bridge circuits. The two of the bridge circuits are capable of transmitting power. A closed-loop circuit is formed by the two of the bridge circuits and the inductance element. The closed-loop circuit includes a capacitor connected between the inductance element and at least one of AC terminals of the two of the bridge circuit. The controller drives switching elements at a switching frequency being higher than a resonant frequency of the closed-loop circuit.